Vibration unit

ABSTRACT

A vibration mechanism ( 300 ) for shaking a tree trunk held between two clamps, for an efficient harvest of the tree-fruits and for preventing damage to the tree-roots and to the tree trunk. The vibration unit comprises two counter-rotating rotors (R) weighted by displaceable weights ( 18, 19 ) and powered, preferably, by at least one hydraulic motor (M). A transmission (T) coupled to the motor and to the rotors, counter-rotates the rotors.

This application is a U.S. National Phase Application Under 35 USC 371of International Application PCT/IL00/00716 (published in English) filedNov. 5, 2000.

TECHNICAL FIELD

The present invention relates to tree-shaking harvesting equipment, andin particular to the vibration generation unit which actuates suchequipment.

BACKGROUND ART

Traditionally, picking fruit and nuts from trees was always donemanually and was inherently labor intensive. With the rise of wages andthe increase of competition in the food supply market, efforts were madeto mechanize the harvesting of trees and to provide for methods that aremore efficient. Because of this quest, tree-shaking machines weredeveloped. Those tree shakers are equipped with a pair of two opposingclamps, which firmly engage a tree on two diametrical sides of thetrunk. The tree shaker also comprises a vibration generation unit thatis connected to the clamps of the tree-shaking machine. Once the clampsare engaged, the tree is shaken to remove the fruit, with the intentthat the inertial forces that will develop on the fruit will exceed thebonding force between the fruit and the stem.

A vibration generation unit is typically driven by a dual oscillationmechanism, which operate substantially independently of one another. Anexample is provided in U.S. Pat. No. 3,338,040 which shakes the tree ina number of different random directions. Such action is undesirable,because some of these directions may cause damage to the tree. Forexample, those directions in which the clamps vibrate tangentially tothe trunk cause transverse shear which can strip tree bark and abradethe stem. Furthermore, two randomly vibration generation units dosometimes oppose one another and cause energy dissipation; orexcessively reinforce one another and thereby exert exaggeratedcompressive forces on the tree.

Efforts to coordinate the action of the two vibration generating units,such as modification of the moment of inertia of the spinning rotatorsresulted in U.S. Pat. Nos. 3,548,578 and 4,903,471. But even thoseimproved devices wrench the trees across a range of directions at once,risking damage to the root system. Experiments were also conducted withthe variation of the frequency of shaking, to reach the naturalresonance frequency of the tree. It was thought that if it would bepossible to reach the maximum amplitude of displacement, then the mostefficient tree harvesting conditions would be s obtained. A limb shakerhaving a variable throttle arrangement that can be adjusted until thegreatest displacement is observed is taught in U.S. Pat. No. 3,650,099.However, with a manual throttle setting device, the shaker was poorlysuited for commercial harvesting.

In a paper of the American Society of Agricultural Engineers, by J. D.Whitney, G. H. Smerage and W. A. Block, No. 0001-2351/90/3304-1066,published in April 1990, there is mention of a shaking system with athree-shaft linear vibrator. As shown in FIG. 1, the elements of thesystem comprise a vibration unit A, a tree clamp C engaging a trunk Band part of the shaker machine D. The vibration unit A consists of threeidentical vertical sprocket wheels mounted side by side on a horizontalframe beam F inside a housing H. One sprocket wheel MS, the middle onefor example, is driven by a motor M, not shown in FIG. 1 for the sake ofclarity, and the other two sprocket wheels, on the sides of the drivensprocket wheel MS, are driven sprockets S. A chain CH couples the threesprocket wheels, with the slack side SS of the chain CH, runningsubstantially in parallel and below the frame beam F. The slack side SSis tensioned by an idler ID. The two driven sprocket wheels S areengaged by the chain CH to rotate in the same direction while the middledriving sprocket MS counter-rotates. This is achieved by running thechain over both side sprocket wheels S but under the driven sprocketwheel MS.

To generate vibrations, the sprocket wheels carry eccentric weights. Asingle weight G is mounted eccentrically on each one of the sprocketwheels S while a double weight 2G is mounted with the same eccentricityon the driven sprocket wheel MS. With reference to FIG. 1, the singleweights G and the double weight 2G are all aligned to the east,according to the directions of the compass card. A force vector equal tothe sum of forces applied by the two single weights G and the one doubleweight 2G is thus applied eastwards.

Assuming that the driven sprocket wheel MS rotates anti-clockwise, thenboth sprocket wheels S will rotate clockwise. FIG. 2 now represents thes vibration unit A after a quarter of a turn of the sprocket wheels,according to the assumed direction of rotation. The single weights G onthe sprocket wheels S now point northwards while the double weight 2Gpoints southwards. The force vector of the sum of forces applied all theweights, namely, two single forces G pointing to the north and onedouble weight 2G directed to the south, now equals zero, and thereby,the upward and the downward forces cancel out.

Another quarter of turn of the sprocket wheels is depicted in FIG. 3.This time all the weights are aligned westwards. The resultant forcevector is thus the same as at the start, as shown in FIG. 1, but in theopposite direction. One more quarter of a turn, not illustrated in adrawing, would result in a rotation of 180 degrees of all the sprocketwheels relative to FIG. 2, whereby the force vector would again sum upto zero. It has thus been shown that the vibration unit A is a linearshaker: theoretically, forces appear only horizontally, in the east towest direction, while no forces are generated vertically, north-south.

In practice however, the results are quite different. First, thevibration unit A is limited to rather slow rotational velocities, due tothe chain drive, which makes it unfit for the harvesting of smallerfruit. Second, the vibration unit A develops severe wear and tear,resulting in costly maintenance expenses. Third, the vibration unit Aengages the tree trunks with its longitudinal axis in the direction ofshaking, thus rendering it very awkward to operate.

Although tree shakers are readily available, their vibration generatingunits still suffer from various drawbacks such as slippage, loss ofrotational synchronization which causes deviation from a single shakingdirection, as well as damage to tree trunks and overall low harvestingefficiency.

For the above-mentioned reasons, there is obviously a need for bettervibration generating units that keep their synchronization, are cheap tomaintain and operate, and are easy to use. Moreover, there is definitelya need for equipment which features high efficiency harvesting and isinexpensive to manufacture.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a vibrationgeneration mechanism for the high efficiency harvesting of trees.

It is another object of the present invention to provide a vibrationgeneration mechanism, which is simple to use and operate.

It is a further object of the present invention to provide a vibrationgeneration mechanism that will not harm the trees during shaking.

It is yet another object of the present invention to provide a unitaryimproved but simple vibration generation mechanism featuring low costsof production, of operation and of maintenance.

Still another object of the present invention is to provide a vibrationgeneration mechanism, which is reliable and long lasting.

It is an object of the present invention to provide a linear vibrationgeneration mechanism for a tree trunk shaker, the shaker comprising apair of clamps for locking on the trunk on opposite sides thereof andthe linear vibration generation mechanism comprising:

at least one motor for providing rotational motion at a predeterminedangular velocity,

a transmission coupled to the at least one motor, the transmission forproviding a counter-rotating motion,

a pair of identical eccentric rotators coupled to the providedcounter-rotating motion, the pair of eccentric rotators rotating inparallel planes and at same angular velocity, and

an enclosure for containing the linear vibration generation mechanism,the enclosure being associated with one clamp of the pair of clamps. Theenclosure is possibly an integral part of one clamp of the pair ofclamps.

It is another object of the present invention to provide a linearvibration mechanism, where the pair of eccentric rotators furthercomprises:

at least one weight, and

an arm having for releasably but fixedly supporting the at least oneweight in adjustable position thereon, and the arm accommodates for thesupport of different at least one weight(s) and allows adjustment of theat least one weight(s) to achieve different identical eccentricity ofthe pair of eccentric rotators.

Another object of the present invention is to provide a way to definethe direction of linear vibration by alignment of the at least oneweight of each one of the pair of eccentric rotators in the desireddirection of vibration.

Yet another object of the present invention is to allow a choice ofmotor from hydraulic motors, electric motors, internal combustion motorsand pneumatic motors, or the selection of a motor built as a hydraulicmotor of the gear-on-gear type, either with spur gears or with helicalgears. It is also possible to have the at least one motor also serves asthe transmission for providing counter-rotating motion. Evidently, thepredetermined angular velocity of the motor is controllable.

Moreover, another object of the present invention is to provide a linearvibration mechanism wherein the at least one hydraulic motor comprises amodification of a conventional gear-on-gear oil pump into a hydraulicmotor, wherein

the conventional gear-on-gear oil pump comprises:

a housing having a first side in parallel and opposite to a second side,the housing also comprising a third side opposite to a fourth side, thefirst side being perpendicular to the third side, the housing beingsealed close, and the housing defining an inside and an outside,

a first drive gear,

a driven gear of the same size as the first drive gear, the first drivegear and the driven gear meshing side-by-side in counter-rotation insidethe housing,

a first driving shaft coextensive and coaxial with the first drive gear,the first driving shaft protruding outside of the first side of thehousing in sealed engagement therewith,

an oil inlet port located amid the third side, and

an oil outlet port located amid the fourth side, and

the at least one hydraulic motor comprises:

the conventional gear-on-gear oil pump,

a second drive gear,

a second driving shaft, the second driving shaft and the second drivegear being of the same size as the first drive gear and the firstdriving shaft, the second drive gear meshing with the first drive gearin replacement of the driven gear, and the second driving shaftprotruding outside of the second side of the housing in sealedengagement therewith, the first driving shaft and the second drivingshaft being parallel to each other,

whereby supply of oil under pressure to the oil inlet portcounter-rotates the first drive gear in mesh with the second drive gearto counter-rotate the first driving shaft and the second driving shaftand thereby creating a hydraulic motor which also serves as thetransmission for providing counter-rotating motion. The gears of thefirst drive gear and of the second drive gear are selected from thegroup consisting of spur gears and helical gears.

Furthermore, it is another object of the present invention to provide avibration generation mechanism where the at least one motor furthercomprises:

an output shaft, and

the transmission further comprises:

a housing comprising a first side and a second side, the second sidebeing opposite to and in parallel with the first side, the housingdefining an inside and an outside, the first side outside supporting theat least one motor with the output shalt thereof entering inside thehousing through the first side and protruding outside of the secondside,

a first gear coupled to the output shaft inside the housing,

a second gear of the same size as the first gear, the second gear andthe first gear meshing side-by-side in counter-rotation inside thehousing, and

a driven shaft coextensive and coaxial with the second gear, the drivenshaft exiting the housing and protruding outside the first side of thehousing, and the output shaft being parallel to the driven shaft,

the housing further accommodating bearings to support the output shaft,the first gear, the second gear and the driven shaft,

whereby rotation of the at least one motor counter-rotates the outputshaft relative to the driven shaft. The housing may be selected from thegroup consisting of an open housing, a closed housing and a sealedhousing.

In addition, it is another object of the present invention to provide avibration generation mechanism where the at least one motor furthercomprises:

a first motor having a first output shaft and a second motor having asecond output shaft, the first motor rotating in direction opposite torotation direction of the second motor, and

the housing further comprising:

the first side outside supporting the first motor and the second sideoutside supporting the second motor,

the first output shaft and the second output shaft penetrating from theside of their respective motor to inside the housing and protruding tothe opposite side outside, the first output shaft and the second outputshaft being parallel, and

the first gear and the second gear being coupled, respectively, to thefirst output shaft and to the second output shaft. In this case, thefirst gear and the second gear synchronize rotation of the first motorand of the second motor.

It is another object of the present invention to provide that the atleast one motor further comprises an output shaft, and the transmissioncomprises:

a housing of rectangular cross-section having a first side, a secondside, a third side and a fourth side, the first side and the third sidebeing opposite to and in parallel with, respectively, the second sideand the fourth side, the sides of the housing defining a housing insideand a housing outside, with the first side outside supporting the atleast one motor with the output shaft thereof penetrating inside thehousing,

a drive pinion coupled to the output shaft inside the housing, the drivepinion being a rotatably mounted bevel gear,

a pair of coaxial parallel bevel gears meshing in perpendicular with thedrive pinion, each one of the pair of bevel gears being rotatablylocated inside the housing, respectively on the third side and on thefourth side,

a pair of coaxial driven shafts protruding outside the housing, each oneof the pair of driven shafts being coupled to each one of the pair ofparallel bevel gears, the output shaft and the pair of driven shaftsresiding in the same plane,

whereby rotation of the output shaft drives the parallel bevel gears incounter-rotation, thereby counter-rotating the pair of driven shafts.The housing is selected from the group consisting of an open housing, aclosed housing and a seated housing.

Still another object of the present invention is to provide a vibrationgeneration mechanism where the at least one motor further comprises:

a first motor having a first output shaft and a second motor having asecond output shaft, the first motor rotating in direction opposite torotation direction of the second motor,

the housing further comprising:

the first side outside supporting the first motor and the second sideoutside supporting the second motor,

the first output shaft and the second output shaft penetrating from theside of their respective motor to inside the housing,

a first drive pinion and a second drive pinion located inside thehousing and coupled respectively, to the first output shaft and to thesecond output shaft, the first drive pinion and the second drive pinionbeing a rotatably mounted bevel gear,

a pair of coaxial parallel bevel gears meshing in perpendicular with thefirst drive pinion and a second drive pinion, each one of the pair ofbevel gears being rotatably located inside the housing, respectively onthe third side and on the fourth side,

a pair of coaxial driven shafts protruding outside the housing, each oneof the pair of driven shafts being coupled to each one of the pair ofparallel bevel gears, the first output shaft and the second output shaftand the pair of driven shafts residing in the same plane,

whereby rotation of the output shaft drives the parallel bevel gears incounter-rotation, thereby counter-rotating the pair of driven shafts. Inthis case also, the first drive pinion and a second drive pinion and thepair of coaxial parallel bevel gears synchronize the rotation of thefirst motor and of the second motor.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to better understand and more fully appreciate the inventionand to see how the same may be carried out in practice, some preferredembodiments will now be described, by way of non-limiting example only,with reference to the accompanying drawing in which:

FIG. 1 is a schematic view of a prior art shaking system with athree-shaft linear vibrator;

FIG. 2 is a detail of FIG. 1 after a quarter of turn rotation of asprocket;

FIG. 3 shows the detail of FIG. 2 after another partial sprocketrotation;

FIG. 4 is a block diagram displaying the elements of the presentinvention;

FIG. 5 shows a schematic of first embodiment of a vibration generationmechanism; in relation to the elements detailed in FIG. 4;

FIG. 6 depicts a second schematic embodiment of the vibration generationmechanism also in accordance with the elements of FIG. 4; and

FIG. 7 illustrates a third schematic embodiment of the presentinvention, likewise based on FIG. 4.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Previous efforts of the present inventors have resulted in a pastinvention disclosed in U.S. Pat. No. 5,473,875, which is incorporatedherewith by reference. There was presented a tree-shaking apparatus witha pair of two separate vibration generation units, each unit with aneccentric rotator and with sensors for sensing the instantaneous angularposition of the eccentric rotator. In addition, the tree shakercomprised control means for rotating both eccentric rotators at auniform rotational speed in opposite direction, which provided apredetermined shaking frequency. More control means coordinated therotation of both eccentric rotators, in response to data provided by theposition-sensing means, to keep the rotation in phase and thereby shakethe tree along a single axis.

The intention was to provide for a tree shaker that would automaticallyselect the optimal parameters of operation to maximize the efficiency ofharvesting. This maximum efficiency was achieved by automaticallymatching of the frequency of tree shaker to the natural resonance of thetree, by choosing the best direction of shaking and by shaking the treealong a single axis. However, field tests proved that application of theprocedure of automatic matching of parameters for tree after tree is tootedious and too time consuming. Test evidence further indicated that thetrees of a same groove all exhibit approximately the same inherentcharacteristic response to shaking. It was thus concluded that it wouldbe practical to provide for a shaker with one single linear vibrationgeneration unit consisting of a sturdy, simple and reliable pair ofcounter-rotating eccentric rotators rotating at exactly the samerotation speed. Accordingly, details of the present invention will besupplied below.

FIG. 4 presents the main elements of a linear vibration generationmechanism for a tree trunk shaker. In general, the vibration generationmechanism is composed of a motor M, for the provision of rotary motion,of a transmission T to produce counter-rotation and of a pair ofeccentric rotators R, to generate vibrations. The motor M derives energyfrom a power supply PS and the output of the eccentric rotators R iscoupled to a pair of clamps C, which clamp the tree trunk and impartvibrations thereto. FIG. 4 thus depicts an autonomous linear vibrationgeneration mechanism with counter-rotating eccentric rotators forshaking tree trunks held in clamps. The vibration generation mechanismcomprises the motor M, the transmission T and the pair of eccentricrotators R designated by the numeral I in FIG. 4.

Both clamps C transmit the vibrations from the vibration generationmechanism to the tree trunk. These clamps C are operated as a powersystem, which is separated from the vibration generation mechanism andwill not be described, as they are not part of the present invention.The following description will be restricted to the vibration generationmechanism I of FIG. 4.

A first embodiment 100 of the vibration generation mechanism is shown inFIG. 5. The pair of eccentric rotators is designated as R, but the motoris indicated by MT, thus motor and transmission, because it serves thedouble purpose of providing for generation and transmission of rotationand also for outputting counter-rotation. The implementation of themotor and transmission MT will now be explained.

To build a motor and transmission element MT, it is easiest to convert ahydraulic pump and to turn it into a hydraulic motor. Hydraulic pumpsare well known components, which will not to be described in detail.Citation is made of the Fluid Power Reference Issue of Machine Design,volume 47, number 22, of Sep. 11, 1975, published by the PentonPublishing Co., of Cleveland, Ohio, USA, that is incorporated herewithby reference. Hydraulic pumps are covered in Section 1, which starts onpage 7 and ends on page 22 inclusive. Best suited for the task aregear-on-gear type pumps, consisting of two identical gears in mesh witheach other, inside a sealed housing. It should be noted that helicalgear motors are also suitable for the task. The first gear of thehydraulic pump, named drive gear or driving gear, is driven by a driveshaft that is an extension of the driving gear. The second gear, calledthe driven gear, is rotated by the drive gear. Both the drive gear andthe driven gear are enclosed in a housing having an oil inlet and an oiloutlet. When the drive shaft is rotated by an external motor, oilsupplied to the oil inlet enters the hydraulic pump and is swept aroundthe periphery of the meshing gears towards the oil outlet, where itexits under pressure. The pair of gears of the pump, which carry thefull power load of the pump, are supported by appropriate bearings. Thehousing of the pump and the driving shaft are sealed to withstand highpressures. Hydraulic pumps are manufactured with either spur gears orhelical gears, but the spur gear configuration, which is preferred, isthe most common.

It will now be explained how a hydraulic pump, which uses the rotationalinput of a motor to generate hydraulic pressure, may be converted to ahydraulic motor that generates rotational motion, when provided withhydraulic pressure. Starting with the hydraulic pump, the driven spurgear is replaced by a drive spur gear of the same size. As both gearsare of the same size, the housing fits. However, the drive gear has adrive shaft that is an extension thereof and therefore, the housing mustbe modified to comprise appropriate bearing support and seals. For thesake of clarity, the bearings and the seals, all well known to the art,are not shown in the drawings.

The result obtained comprises a housing with an inlet port and an outletport and a pair of drive gears, inside the housing, which both extend indrive shafts protruding to the outside of the housing. Now, whenhydraulic pressure is supplied to the oil inlet, hydraulic fluid flowsthrough the periphery of the spur gears to the oil outlet, rotating bothgears simultaneously, and thereby also rotating both shafts. As bothgear are in mesh, they counter-rotate and their corresponding shaftsfollow suit.

The hydraulic pump has thus been modified into a hydraulic motor with aninherent counter-rotating capability. Evidently, a gear-on-gearhydraulic motor may be transformed in the same manner, to provide thesame results. FIG. 5 is a schematic rendering of the first embodiment100, with a cross-section cut through the housing 10, The oil inlet andthe oil outlet are deleted for the sake of clarity. Two spur gears 12and 13 extend into, respectively, drive shafts 14 and 15 forming rotatorshafts. In the same symmetric fashion, two arms 16 and 17 are fixedlycoupled, respectively, to the drive or rotator shafts 14 and 15, bymeans well known to the art. The arms 16 and 17 are made to supportfixedly, but releasably and adjustably, two weights, respectively, 18and 19, again, by means well known to the art. As the connection betweenthe weights 18 and 19 is adjustable, the weights, 18, 19, may berelocated along the length of the arms 16 and 17. These weights 18 and19 may also be replaced by other weights, either heavier or lighter.

The parameters controlling the output of the vibration generationmechanism may be varied in different ways. First, by controlling thevolumetric flow of oil supplied to the motor MT, which willproportionally alter the delivered rotational velocity. Therefore, thehigher the flow rate, the higher the frequency of the vibrations.Second, the distance between each weight 18 and 19, and its respectivedrive or rotator shafts 14 and 15, and third, the mass of each one ofthe weights 18 and 19, mass which may be augmented or reduced.

A second embodiment 200 of the vibration generation mechanism will bedescribed with the help of FIG. 6. The three elements, namely, a motorM, a transmission T for generating counter-rotating motion, and a pairof eccentric rotators R are present, but as three separate entities. Amotor M of any kind, but preferably a hydraulic motor, is mountedoutside the housing 20 and is coupled to the transmission T. A pair ofmeshing gears 22 and 23, either helical gears or preferably spur gears,extend each, respectively, in rotator shafts 24 and 25. These gears 22and 23 are supported by bearings and seals (not shown in FIG. 5) on thehousing 20. It should be noted that the rotator shaft 25 is shown asbeing the output shaft of the motor M. Another option would be to couplethe output shaft of the motor M to the rotator shaft 24. The two rotatorshafts 24 and 25 are coupled to the two eccentric rotators R in the samemanner as was described above for the embodiment 100. Still anotheroption would be to provide for two motors M, one for each rotator shaft24 and 25 respectively. The task of the meshing gears 22 and 23 is nowonly one of synchronizing both motors M and not anymore to carry loads.

In contrast with the first embodiment 100, the motor M of the secondembodiment 200 is located outside of the housing 20, whereby it iseasier to perform motor maintenance and to replace the motor M. Inaddition, the transmission mechanism T may be sealed inside the housing20 awhile the single or pair of motors M remain outside the housing 20,for better cooling and ease of maintenance.

A third embodiment 300 of the linear vibration generation mechanism isshown in FIG. 7. Here again, the three elements, motor M, transmission Tand eccentric rotators R are separate elements, as opposed to the firstembodiment 100.

A motor M, preferably a hydraulic motor, although other motors aresuitable, is mounted on a housing 30. The output shaft 31 of the motoris coupled to a bevel gear drive pinion 32 and is supported by bearings(not shown in FIG. 7) on the housing 30. A pair of coaxial parallelbevel gears 34 and 35 mesh in parallel planes perpendicular with theplane of the drive pinion 32. Each one of the bevel gears 34 and 35meshes on diametrically opposed sides of the drive pinion 32. The bevelgears 34 and 35 further extend in, respectively, aligned driven orrotator shafts 36 and 37. The rotator shafts 36 and 37 are eachsupported by bearings (not shown in FIG. 7) mounted on the housing 30.The output shaft 31 is perpendicular to the driven rotator shafts 36 and37, but all the three shafts 31, 36 and 37 reside in the same horizontalplane.

Operation of the motor M rotates the output shaft 31, which drives thedrive pinion 32. In turn, the pinion drive 32 rotates both coaxialparallel bevel gears 34 and 35, but those parallel bevel gearscounter-rotate as they are both driven by the same pinion drive 32. As aresult, the driven or rotator shafts 36 and 37 counter-rotate. Similarto the embodiment 200, the pair of eccentric rotators R is coupled tothe driven or rotator shafts 36 and 37. Here too, a second motor M maybe mounted on the housing 30, opposite to the first motor M. such anoption calls for the addition of a second drive pinion 32, in oppositeand in parallel with the first drive pinion 32. The two drive pinions 32and the two bevel gears 34 and 35 would form a rectangle. Still anotheroption allows the gears to only synchronize the rotation of the twomotors M without carrying loads, by coupling each motor M to one of thepair of parallel bevel gears 34 and 35 instead of to the pinion gears32. Evidently, a single pinion gears 32 would suffice forsynchronization.

While preferred embodiments of the invention have been described shownand described in detail, it should be apparent that many modificationsand variations thereto are possible, all of which fall within the truespirit and scope of the invention. For example, more than one motor maybe used to provide for redundancy or greater output power. Also, otherconfigurations are possible for the arms of the eccentric rotators, suchbeing in the shape of a disk, of a sector, or in another shape.

It will be appreciated by persons skilled in the art that the presentinvention is not limited to what has been particularly shown anddescribed above. Rather the scope of the present invention is definedonly by the claims, which follow.

What is claimed is:
 1. A linear vibration generation mechanism for atree trunk shaker comprising a pair of clamps for locking on the trunkon opposite sides thereof, the mechanism comprising: at least one motorfor providing rotational motion at a predetermined controllable angularvelocity, a pair of identical eccentric rotators coupled to the at leastone motor, the pair of eccentric rotators rotating in parallel planesand at the same angular velocity, each one rotator comprising a rotatorshaft, an enclosure for containing the mechanism, the enclosure being anintegral part of one clamp out of the pair of clamps, and the at leastone motor being a hydraulic motor of the gear-on-gear type, with eachone gear being coupled to one out of the pair of identical eccentricrotators by the rotor shaft, wherein the at least one hydraulic motorserves for provision and for transmission of rotational andcounter-rotating motion.
 2. The mechanism according to claim 1, whereineach one out of the pair of eccentric rotators further comprises: atleast one weight, and an arm for releasably but fixedly supportingthereon the at least one weight in adjustable position.
 3. The mechanismaccording to claim 2, the arm further comprising: accommodation forsupporting of different at least one weight(s).
 4. The mechanismaccording to the claim 3, the arm further comprising: accommodation forthe adjustment of the position of the at least one weight to achievedifferent identical eccentricity of the pair of eccentric rotators. 5.The mechanism according to claim 3, wherein: the direction of linearvibration is defined by aligning the at least one weight of each one outof the pair of eccentric rotators in the desired direction of vibration.6. The mechanism according to the claim 2, the arm further comprising:accommodation for the adjustment of the position of the at least oneweight to achieve different identical eccentricity of the pair ofeccentric rotators.
 7. The mechanism according to claim 6, wherein: thedirection of linear vibration is defined by aligning the at least oneweight of each one out of the pair of eccentric rotators in the desireddirection of vibration.
 8. The mechanism according to claim 2, wherein:the direction of linear vibration is defined by aligning the at leastone weight of each one out of the pair of eccentric rotators in thedesired direction of vibration.
 9. The mechanism according to claim 2,wherein: the direction of linear vibration is defined by aligning the atleast one weight of each one out of the pair of eccentric rotators inthe desired direction of vibration.
 10. The mechanism according to claim1 wherein the at least one hydraulic motor comprises: a conventionalgear-on gear type oil pump, comprising: a housing having a first side inparallel and opposite to a second side, the housing also comprising athird side opposite to a fourth side, the first side being perpendicularto the third side, the housing being sealed close, and the housingdefining an inside and an outside, a first drive gear, a driven gear ofthe same size as the first drive gear, the first drive gear and thedriven gear meshing side-by-side in counter-rotation inside the housing,a first driving shaft coextensive and coaxial with the first drive gearthe first driving shaft protruding outside of the first side of thehousing in sealed engagement therewith, an oil inlet port located amidthe third side, and an oil outlet port located amid the fourth side, theat least one hydraulic motor further comprising: the conventionalgear-on-gear oil pump modified to comprise: a second driving shaft ofthe same size as the first driving shaft, the second driving shaft beingcoupled to the driven gear for operation as a second driving gear, andthe second driving shaft protruding outside the second side of thehousing in sealed engagement therewith, the first driving shaft and thesecond driving shaft being parallel to each other, whereby supply of oilunder pressure to the oil inlet port rotates in mesh the first and thesecond drive gears in counter-rotation, thereby counter-rotating thefirst and the second driving shafts coupled to the rotator shaft of eachone out of the pair of identical eccentric rotators.
 11. The at leastone hydraulic motor according to claim 10, wherein: the gear-on geartype is selected from the group of types consisting of spur gears and ofhelical gears.
 12. The mechanism according to claim 1, wherein: thegear-on gear type is selected from the group of types consisting of spurgears and of helical gears.
 13. The mechanism according to the claim 1,wherein: the at least one motor further comprising comprises an outputshaft, and a transmission is coupled to the output shaft of the at leastone motor for transmission of motion, and the mechanism beingcharacterized by the transmission further comprising: housing comprisinga first side and a second side, the second side being opposite to and inparallel with the first side, the housing defining an inside and anoutside, the first side outside supporting the at least one motor withthe output shaft thereof entering inside the housing, through the firstside and protruding outside of the second side, a first gear coupledinside the housing to the output shaft penetrating the housing andexiting therefrom to protrude outside the second side, a second gear ofthe same size as the first gear, the second gear and the first gearmeshing side-by-side in counter-rotation inside the housing, and adriven shaft coextensive and coaxial with the second gear, the drivenshaft exiting the housing to protrude outside the first side in parallelto the output shaft, the protruding end of each one of the output shaftand of the driven shaft being coupled to one out of the pair ofidentical eccentric rotators, and bearings accommodated in the housingto support the output shaft, the first gear, the second gear and thedriven shaft whereby rotation of the at least one motor rotates theoutput shaft and counter-rotates the driven shaft, for transmission ofmotion and of counter-rotating motion to each one rotator shaft out ofthe pair of identical eccentric rotators.
 14. The mechanism according toclaim 13, wherein: the at least one motor comprises a first motor havinga first output shaft and a second motor having a second output shaft,the first motor rotating in a direction opposite to the second motor,and the housing further comprising: the first side outside supportingthe first motor and the second side outside supporting the second motor,the first output shaft and the second output shaft penetrating from theside of their respective motor to inside the housing and protruding outof the opposite side outside, the first output shaft and the secondoutput shaft being parallel, and the first gear and the second gearbeing coupled inside the housing, respectively, to the first outputshaft and to the second output shaft, whereby the first gear and thesecond gear synchronize opposite rotation, of the first motor and of thesecond motor.
 15. The mechanism according to the claim 13, wherein: thehousing is selected from the group consisting of an open housing, aclosed housing and a sealed housing.
 16. The mechanism according toclaim 1, wherein: the at least one motor further comprises an outputshaft, and a transmission is coupled to the output shaft fortransmission of motion, and the mechanism being characterized by thetransmission further comprising: a housing of rectangular cross-sectioncomprising a first side, a second side, a third side and a fourth sidedefining a housing inside and a housing outside, the first side and thesecond side being opposite and in parallel with, respectively, the thirdside and the fourth side, with the first side outside supporting the atleast one motor with the output shaft thereof penetrating inside thehousing, a drive pinion coupled to the output shaft inside the housing,the drive pinion being a bevel gear, a pair of coaxial parallel bevelgears meshing in perpendicular with the drive pinion, each one of thepair of bevel gears being rotatably supported inside the housing,respectively on the third side and on the fourth side, a pair of coaxialdriven shafts with each one driven shaft out of the pair of coaxialdriven shafts being coupled to each one out of the pair of parallelbevel gears, each one out of the pair of driven shafts protrudingoutside the housing and being coupled to one out of the pair ofidentical eccentric rotators, whereby rotation of the output shaftdrives the parallel bevel gears in counter-rotation, therebycounter-rotating the pair of driven shafts for transmission ofrotational motion and of counter-rotation to each one rotator shaft outof the pair of identical rotators.
 17. The mechanism according to claim16, wherein: the at least one motor further comprises a first motorhaving a first output shaft and a second motor having a second outputshaft, the first motor rotating in a direction opposite to the secondmotor, and the housing further comprising: the first side outsidesupporting the first motor and the second side outside supporting thesecond motor, the first output shaft and the second output shaftpenetrating from the side of their respective motor to inside thehousing, a first drive pinion and a second drive pinion located insidethe housing and coupled respectively, to the first output shaft and tothe second output shaft, the first drive pinion and a second drivepinion being a bevel gear, a pair of coaxial parallel bevel gearsmeshing in perpendicular with the first drive pinion and a second drivepinion, each one of the pair of bevel gears being rotatably supportedinside the housing, respectively on the third side and on the fourthside, and a pair of coaxial driven shafts protruding outside thehousing, each one out of the pair of coaxial driven shafts being coupledto each one out of the pair of parallel bevel gears, each one drivenshaft being coupled to one out of the pair of identical rotators,whereby rotation of the output shafts drive the parallel bevel gears incounter-rotation, thereby counter-rotating the pair of driven shafts.18. The mechanism according to claim 17, wherein: the first drive pinionand a second drive pinion and the pair of coaxial parallel bevel gearssynchronize rotation of the first motor and of the second motor.
 19. Themechanism according to the claim 16, wherein: the housing is selectedfrom the group consisting of an open housing, a closed housing and asealed housing.